New Delhi metallo-β-lactamase: a cautionary tale

Molecular characterization of NDM-1-producing Pseudomonas aeruginosa isolates from hospitalized patients in Iran

Background

The emergence of carbapenem-resistant Pseudomonas aeruginosa is one of the most important challenges in a healthcare setting. The aim of this study is double-locus sequence typing (DLST) typing of bla_NDM-1 positive P. aeruginosa isolates.

Methods

Twenty-nine bla_NDM-1 positive isolates were collected during three years of study from different cities in Iran. Modified hodge test (MHT), double-disk synergy test (DDST) and double-disk potentiation test (DDPT) was performed for detection of carbapenemase and metallo-beta-lactamase (MBL) producing bla_NDM-1 positive P. aeruginosa isolates. The antibiotic resistance genes were considered by PCR method. Clonal relationship of bla_NDM-1 positive was also characterized using DLST method.

Results

Antibiotic susceptibility pattern showed that all isolates were resistant to imipenem and ertapenem. DDST and DDPT revealed that 15/29 (51.8%) and 26 (89.7%) of bla_NDM-1 positive isolates were MBL producing isolates, respectively. The presence of bla_OXA-10,bla_VIM-2, bla_IMP-1 and bla_SPM genes were detected in 86.2%, 41.4%, 34.5% and 3.5% isolates, respectively. DLST typing results revealed the main cluster were DLST 25-11 with 13 infected or colonized patients.

Conclusions

The presence of bla_NDM-1 gene with other MBLs encoding genes in P. aeruginosa is a potential challenge in the treatment of microorganism infections. DLST showed partial diversity among 29 bla_NDM-1 positive isolates.

Molecular Epidemiology of Carbapenemases in Enterobacteriales from Humans, Animals, Food and the Environment

The Enterobacteriales order consists of seven families including Enterobacteriaceae, Erwiniaceae, Pectobacteriaceae, Yersiniaceae, Hafniaceae, Morganellaceae, and Budviciaceae and 60 genera encompassing over 250 species. The Enterobacteriaceae is currently considered as the most taxonomically diverse among all seven recognized families. The emergence of carbapenem resistance (CR) in Enterobacteriaceae caused by hydrolytic enzymes called carbapenemases has become a major concern worldwide. Carbapenem-resistant Enterobacteriaceae (CRE) isolates have been reported not only in nosocomial and community-acquired pathogens but also in food-producing animals, companion animals, and the environment. The reported carbapenemases in Enterobacteriaceae from different sources belong to the Ambler class A (bla_KPC), class B (bla_IMP, bla_VIM, bla_NDM), and class D (bla_OXA-48) β-lactamases. The carbapenem encoding genes are often located on plasmids or associated with various mobile genetic elements (MGEs) like transposons and integrons, which contribute significantly to their spread. These genes are most of the time associated with other antimicrobial resistance genes such as other β-lactamases, as well as aminoglycosides and fluoroquinolones resistance genes leading to multidrug resistance phenotypes. Control strategies to prevent infections due to CRE and their dissemination in human, animal and food have become necessary. Several factors involved in the emergence of CRE have been described. This review mainly focuses on the molecular epidemiology of carbapenemases in members of Enterobacteriaceae family from humans, animals, food and the environment.

Antibiogram and recent incidence of multi-drug resistant carbapenemase producing Escherichia coli isolated from paediatric patients

Objective:

To gauge the recent breadth of MDR E. coli along with antibiogram of carbapenemase producing (CP) E. coli among children from an institute which receives patients from all over Punjab.

Methods:

The bacterial strains of E. coli isolated from various specimens of patients were collected from April 2017 to August 2018 and processed using standard biochemical tests and API 20E system (bioMerieux). Phenotypic screening for CP E. coli was done by the modified Hodge test, whereas antibiotic susceptibility testing was done with Kirby-Bauer disc diffusion technique.

Results:

Total of 6,468 bacterial strains were isolated, out of which 1,552 (24%) were E. coli. Carbapenem resistance was observed in 245 (16%) strains, amongst which 113 (46%) were confirmed to be CP. E. coli isolated from males were higher as compared to females (p<0.05). Majority of the organisms were isolated from blood (37.2%) samples. The hospital discharged about 65% of patients, while 23% left against medical advice. Overall MDR amongst E. coli was 93.26%. Colistin sulphate (15.9%) and nitrofurantoin (16.8%) showed the most efficacy followed by amikacin (15%) and fosfomycin (10.6%).

Conclusion:

The isolation of high number of MDR E. coli amongst the paediatric patients is worrisome, which could serve as a potential source of horizontal genes transfer to other genera.

Bacteriophages To Sensitize a Pathogenic New Delhi Metallo β-Lactamase-Positive Escherichia coli to Solar Disinfection

Bacteriophages active against a New Delhi metallo beta lactamase (NDM)-positive E. coli PI-7 were isolated from municipal wastewater and tested for their lytic effect against the bacterial host. Bacteriophages were highly specific to E. coli PI-7 when tested for host-range. After determining host-specificity, bacteriophages were tested for their ability to sensitize E. coli PI-7 to solar irradiation. Solar irradiation coupled with bacteriophages successfully reduced the length of the lag-phase for E. coli PI-7 from 4 h to 2 h in buffer solution. The reduction of lag-phase length was also observed in filtered wastewater effluent and chlorinated effluent. Previously, we found through gene expression analysis that cell wall, oxidative stress, and DNA repair functions played a large role in protecting E. coli PI-7 against solar damage. Here, gene expression analysis of bacteriophage-supplemented solar-irradiated E. coli PI-7 revealed downregulation of cell wall functions. Downregulation of functions implicated in scavenging and detoxifying reactive oxygen species, as well as DNA repair genes, was also observed in bacteriophage-supplemented solar-irradiated E. coli PI-7. Moreover, solar irradiation activates recA, which can induce lytic activity of bacteriophages. Overall, the combined treatment led to gene responses that appeared to make E. coli PI-7 more susceptible to solar disinfection and bacteriophage infection. Our findings suggest that bacteriophages show good potential to be used as a biocontrol tool to complement solar irradiation in mitigating the persistence of antibiotic-resistant bacteria in reuse waters.

High Prevalence of blaNDM-1, blaVIM, qacE, and qacEΔ1 Genes and Their Association with Decreased Susceptibility to Antibiotics and Common Hospital Biocides in Clinical Isolates of Acinetobacter baumannii

The objective of this study was to evaluate the susceptibility of metallo-β-lactamase (MBL)-producing Acinetobacter baumannii (A. baumannii) clinical isolates to biocides. We also determined the prevalence and correlation of efflux pump genes, class 1 integron and MBL encoding genes. In addition, bla_VIM, bla_NDM-1, qacE and qacEΔ1 nucleotide sequence analysis was performed and compared to sequences retrieved from GenBank at the National Center for Biotechnology Information database. A. baumannii had a resistance rate to carbapenem of 71.4% and 39.3% and was found to be a MBL producer. The minimum inhibitory concentrations (MICs) of chlorhexidine and cetrimide were higher than the recommended concentrations for disinfection in 54.5% and 77.3% of MBL-positive isolates respectively and their MICs were significantly higher among qac gene-positive isolates. Coexistence of qac genes was detected in 68.1% and 50% of the isolates with bla_VIM and bla_NDM-1 respectively. There was a significant correlation between the presence of qac genes and MBL-encoding bla_VIM and bla_NDM-1 genes. Each of the bla_NDM-1, bla_VIM, qacE and qacEΔ1 DNA sequences showed homology with each other and with similar sequences reported from other countries. The high incidence of Verona integron-encoded metallo-β-lactamases (VIM) and New-Delhi-metallo-β-lactamase (NDM) and qac genes in A.baumannii highlights emerging therapeutic challenges for being readily transferable between clinically relevant bacteria. In addition reduced susceptibility to chlorhexidine and cetrimide and the potential for cross resistance to some antibiotics necessitates the urgent need for healthcare facilities to periodically evaluate biocides efficacy, to address the issue of antiseptic resistance and to initiate a “biocidal stewardship”.

Inactivation and Gene Expression of a Virulent Wastewater Escherichia coli Strain and the Nonvirulent Commensal Escherichia coli DSM1103 Strain upon Solar Irradiation

This study examined the decay kinetics and molecular responses of two Escherichia coli strains upon solar irradiation. The first is E. coli PI-7, a virulent and antibiotic-resistant strain that was isolated from wastewater and carries the emerging NDM-1 antibiotic resistance gene. The other strain, E. coli DSM1103, displayed lower virulence and antibiotic resistance than E. coli PI-7. In a buffer solution, E. coli PI-7 displayed a longer lag phase prior to decay and a longer half-life compared with E. coli DSM1103 (6.64 ± 0.63 h and 2.85 ± 0.46 min vs 1.33 ± 0.52 h and 2.04 ± 0.36 min). In wastewater, both E. coli strains decayed slower than they did in buffer. Although solar irradiation remained effective in reducing the numbers of both strains by more than 5-log₁₀ in <24 h, comparative genomics and transcriptomics revealed differences in the genomes and overall regulation of genes between the two E. coli strains. A wider arsenal of genes related to oxidative stress, cellular repair and protective mechanisms were upregulated in E. coli PI-7. Subpopulations of E. coli PI-7 expressed genes related to dormancy and persister cell formation during the late decay phase, which may have accounted for its prolonged persistence. Upon prolonged solar irradiation, both E. coli strains displayed upregulation of genes related to horizontal gene transfer and antibiotic resistance. Virulence functions unique to E. coli PI-7 were also upregulated. Our findings collectively indicated that, whereas solar irradiation is able to reduce total cell numbers, viable E. coli remained and expressed genes that enable survival despite solar treatment. There remains a need for heightened levels of concern regarding risks arising from the dissemination of E. coli that may remain viable in wastewater after solar irradiation.

Isolation and Characterization of NDM-Positive Escherichia coli from Municipal Wastewater in Jeddah, Saudi Arabia

The emergence of resistance to last-resort antibiotics is a public health concern of global scale. Besides direct person-to-person propagation, environmental pathways might contribute to the dissemination of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs). Here, we describe the incidence of bla_NDM-1, a gene conferring resistance to carbapenems, in the wastewater of the city of Jeddah, Saudi Arabia, over a 1-year period. bla_NDM-1 was detected at concentrations ranging from 10⁴ to 10⁵ copies/m³ of untreated wastewater during the entire monitoring period. These results indicate the ubiquity and high incidence of bla_NDM-1 in the local wastewater. To track the bacteria carrying bla_NDM-1, we isolated Escherichia coli PI7, a strain of sequence type 101 (ST101), from wastewater around the Hajj event in October 2013. Genome sequencing of this strain revealed an extensive repertoire of ARGs as well as virulence and invasive traits. These traits were further confirmed by antibiotic resistance profiling and in vitro cell internalization in HeLa cell cultures. Given that this strain remains viable even after a certain duration in the sewerage, and that Jeddah lacks a robust sanitary infrastructure to fully capture all generated sewage, the presence of this bacterium in the untreated wastewater represents a potential hazard to the local public health. To the best of our knowledge, this is the first report of a bla_NDM-1-positive E. coli strain isolated from a nonnosocomial environment in Saudi Arabia and may set a priority concern for the need to establish improved surveillance for carbapenem-resistant E. coli in the country and nearby regions.

Acinetobacter calcoaceticus from a fatal case of pneumonia harboring bla(NDM-1) on a widely distributed plasmid

BACKGROUND

We have recovered one bla(NDM-1)-harboring bacterial strain, designated as XM1570, from a sputum sample obtained from a fatal case of pneumonia in China.

METHODS

Biochemical profiling, 16S rRNA sequencing and antimicrobial susceptibility testing were performed. Conjugation experiments were conducted to determine transmissibility of resistance. Pulsed-field gel electrophoresis and whole genome sequencing were performed to identify strain-specific features.

RESULTS

The isolate XM1570 was identified as Acinetobacter calcoaceticus. Whole genome sequencing identified two plasmids, pXM1 and pXM2. Comparative analysis showed >99% similarity between XM1570 and A. calcoaceticus PHEA-2. Plasmid pXM1 carried the carbapenemase gene bla(NDM-1) and displayed high homology with previously described plasmids isolated from different Acinetobacter spp., which were collected from human or livestock distributed in China and worldwide. The bla(NDM-1) gene was located on this conjugative plasmid in a transposon-like region flanked by two copies of the insertion sequence ISAba125; and resistance to all tested β-lactams was observed. Transferability of resistance from pXM1 to the transconjugants was identified. Plasmid pXM2 had an insertion sequence ISAba125 and a -35 region of the bla NDM-1 gene promoter but the bla NDM-1 gene was not present. A chromosomally located carbapenemase-encoding gene bla OXA-75 was detected; however, this gene was interrupted by an insertion sequence ISAba22 belonging to IS3 family.

CONCLUSIONS

Location of bla(NDM-1) on different self-transmissible plasmids could facilitate geographically broad dissemination and host range expansion of the bla(NDM-1) gene via horizontal gene transfer. Our findings of this normally environmental species A. calcoaceticus XM1570 further underline the significant clinical challenge and the essential need for surveillance including molecular methods and plasmid analyses.

An enzoinformatics study for prediction of efficacies of three novel penem antibiotics against New Delhi metallo-β-lactamase-1 bacterial enzyme

New Delhi metallo-beta-lactamase (NDM-1) is a beta-lactamase (class B carbapenemase) containing Zn(2+) and other divalent cations as cofactors which possesses the ability to inactivate all beta lactams (including carbapenems) except aztreonam by catalyzing the hydrolytic cleavage of the substrate amide bond. Carbapenemases are either serine enzymes or metallo-β-lactamases (MBLs) that utilize at least one zinc ion for hydrolysis. The present study describes the molecular interaction of carbapenems (Imipenem, Meropenem, Ertapenem, Doripenem, Panipenem, Biapenem, Razupenem, Faropenem, Tebipenem and Tomopenem) with NDM-1, β-lactamase enzyme. Docking between NDM-1 and each of these carbapenems (separately) was performed using 'Autodock4.2'.

An enzoinformatics study for prediction of efficacies of three novel penem antibiotics against New Delhi metallo-β-lactamase-1 bacterial enzyme

New Delhi metallo-beta-lactamase (NDM-1) is a beta-lactamase (class B carbapenemase) containing Zn2+ and other divalent cations as cofactors which possesses the ability to inactivate all beta lactams (including carbapenems) except aztreonam by catalyzing the hydrolytic cleavage of the substrate amide bond. Carbapenemases are either serine enzymes or metallo-β-lactamases (MBLs) that utilize at least one zinc ion for hydrolysis. The present study describes the molecular interaction of carbapenems (Imipenem, Meropenem, Ertapenem, Doripenem, Panipenem, Biapenem, Razupenem, Faropenem, Tebipenem and Tomopenem) with NDM-1, β-lactamase enzyme. Docking between NDM-1 and each of these carbapenems (separately) was performed using 'Autodock4.2'.

Enterobacteriaceae isolates carrying the New Delhi metallo-β-lactamase gene in Yemen

Ten carbapenem-resistant Enterobacteriaceae (eight Klebsiella pneumoniae isolates and two Enterobacter cloacae) isolates from Yemen were investigated using in vitro antimicrobial susceptibility testing, phenotypic carbapenemase detection, multilocus sequence typing (MLST) and replicon typing. Carbapenemase, extended-spectrum β-lactamase (ESBL) and plasmid-mediated quinolone resistance determinant genes were identified using PCR and sequencing. All of the 10 carbapenem-resistant Enterobacteriaceae were resistant to β-lactams, tobramycin, ciprofloxacin and cotrimoxazole. Imipenem, doripenem and meropenem MICs ranged from 2 to >32 mg l(-1) and ertapenem MICs ranged from 6 to >32 mg l(-1). All of the K. pneumoniae isolates showed ESBL activity in phenotypic tests. Genes encoding blaNDM were detected in all strains. All K. pneumoniae strains produced CTX-M-15 ESBL and SHV β-lactamases. TEM-1 β-lactamase was detected in seven isolates. Nine isolates were qnr positive including QnrB1, QnrA1 and QnrS1, and six isolates produced AAC-6'-Ib-cr. MLST identified five different sequence types (STs): ST1399, ST147, ST29, ST405 and ST340. Replicon typing showed the presence of IncFII1K plasmids in four transformants. To the best of our knowledge, this is the first report of NDM-1-producing Enterobacteriaceae isolates in Yemen.

New Delhi Metallo-beta-lactamase around the world: An eReview using Google Maps

Gram-negative carbapenem-resistant bacteria, in particular those producing New Delhi Metallo-beta-lactamase-1 (NDM-1), are a major global health problem. To inform the scientific and medical community in real time about worldwide dissemination of isolates of NDM-1-producing bacteria, we used the PubMed database to review all available publications from the first description in 2009 up to 31 December 2012, and created a regularly updated worldwide dissemination map using a web-based mapping application. We retrieved 33 reviews, and 136 case reports describing 950 isolates of NDM-1-producing bacteria. Klebsiella pneumoniae (n= 359) and Escherichia coli (n=268) were the most commonly reported bacteria producing NDM-1 enzyme. Several case reports of infections due to imported NDM-1 producing bacteria have been reported in a number of countries, including the United Kingdom, Italy, and Oman. In most cases (132/153, 86.3%), patients had connections with the Indian subcontinent or Balkan countries. Those infected were originally from these areas, had either spent time and/or been hospitalised there, or were potentially linked to other patients who had been hospitalised in these regions. By using Google Maps, we were able to trace spread of NDM-1-producing bacteria. We strongly encourage epidemiologists to use these types of interactive tools for surveillance purposes and use the information to prevent the spread and outbreaks of such bacteria.

Epidemiology of carbapenemase-producing Enterobacteriaceae and Acinetobacter baumannii in Mediterranean countries

The emergence and global spread of carbapenemase-producing Enterobacteriaceae and Acinetobacter baumannii are of great concern to health services worldwide. These β-lactamases hydrolyse almost all β-lactams, are plasmid-encoded, and are easily transferable among bacterial species. They are mostly of the KPC, VIM, IMP, NDM, and OXA-48 types. Their current extensive spread worldwide in Enterobacteriaceae is an important source of concern. Infections caused by these bacteria have limited treatment options and have been associated with high mortality rates. Carbapenemase producers are mainly identified among Klebsiella pneumoniae, Escherichia coli, and A. baumannii and still mostly in hospital settings and rarely in the community. The Mediterranean region is of interest due to a great diversity and population mixing. The prevalence of carbapenemases is particularly high, with this area constituting one of the most important reservoirs. The types of carbapenemase vary among countries, partially depending on the population exchange relationship between the regions and the possible reservoirs of each carbapenemase. This review described the epidemiology of carbapenemases produced by enterobacteria and A. baumannii in this part of the world highlighting the worrisome situation and the need to screen and detect these enzymes to prevent and control their dissemination.

Global spread of antibiotic resistance: the example of New Delhi metallo-β-lactamase (NDM)-mediated carbapenem resistance

The rapidity with which new types of antibiotic resistance can disseminate globally following their initial emergence or recognition is exemplified by the novel carbapenemase New Delhi metallo-β-lactamase (NDM). The first documented case of infection caused by bacteria producing NDM occurred in 2008, although retrospective analyses of stored cultures have identified the gene encoding this enzyme (blaNDM) in Enterobacteriaceae isolated in 2006. Since its first description, NDM carbapenemase has been reported from 40 countries worldwide, encompassing all continents except South America and Antarctica. The spread of NDM has a complex epidemiology involving the spread of a variety of species of NDM-positive bacteria and the inter-strain, inter-species and inter-genus transmission of diverse plasmids containing blaNDM, with the latter mechanism having played a more prominent role to date. The spread of NDM illustrates that antibiotic resistance is a public health problem that transcends national borders and will require international cooperation between health authorities if it is to be controlled.

Emergence of multidrug-resistant NDM-1-producing Gram-negative bacteria in Bangladesh

The main objective of this study was to investigate the prevalence of bla (NDM-1) in Gram-negative bacteria in Bangladesh. In October 2010 at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) laboratories, 1,816 consecutive clinical samples were tested for imipenem-resistant Gram-negative organisms. Imipenem-resistant isolates were tested for the bla (NDM-1) gene. Among 403 isolates, 14 (3.5 %) were positive for bla (NDM-1), and the predominant species were Klebsiella pneumoniae, Acinetobacter baumannii, and Escherichia coli. All bla (NDM-1)-positive isolates were resistant to multiple antibiotics. Among β-lactamase genes, bla (CTX-M-1-group) was detected in ten isolates (eight bla (CTX-M-15)), bla (OXA-1-group) in six, bla (TEM) in nine, bla (SHV) in seven, and bla (VIM) and bla (CMY) in two isolates each. The 16S rRNA methylase gene, armA, was detected in five K. pneumoniae isolates and in one E. coli isolate. rmtB and rmtC were detected in a Citrobacter freundii and two K. pneumoniae isolates, respectively. qnr genes were detected in two K. pneumoniae isolates (one qnrB and one qnrS) and in an E. coli isolate (qnrA). Transferable plasmids (60-100 MDa) carrying bla (NDM-1) were detected in 7 of the 11 plasmid-containing isolates. Pulsed-field gel electrophoresis (PFGE) analysis grouped K. pneumoniae isolates into three clusters, while E. coli isolates differed significantly from each other. This study reports that approximately 3.5 % of Gram-negative clinical isolates in Bangladesh are NDM-1-producing.

New Delhi metallo-β-lactamase (NDM-1): an update

New Delhi metallo-β-lactamase (NDM-1) is a novel broad spectrum carbapenemase with ability to inactivate all β-lactams except aztreonam. However, most of the NDM-1-producers also produce aztreonam hydrolysing-β-lactamases thereby making these pathogens absolutely resistant to all β-lactams. The bla(NDM-1) gene encodes a 27.5 kDa protein of 269 amino acids. It shares very little identity with other metallo-β-lactamases. Maximum identity has been observed to VIM-1/VIM-2 (32.4%). This mini-review is an update of the scientific literature for the said enzyme. Following the recommendation of David livermore, we further propose to combine "aztreonam" and "inhibitor of the most frequently encountered aztreonam hydrolysing-β-lactamases in a given setting" as a possible strategy against NDM-1-producers. The inhibitor should be 'versatile' as well, i.e. it should have the ability to inhibit most of the variants of aztreonam hydrolysing-β-lactamases prevalent in the concerned setting. We strongly recommend surveillance studies using aztreonam/NXL-104-combination against NDM-1-producing pathogens in different geographical regions across the globe.

The emerging NDM carbapenemases

Carbapenems were the last β-lactams retaining near-universal anti-Gram-negative activity, but carbapenemases are spreading, conferring resistance. New Delhi metallo-β-lactamase (NDM) enzymes are the latest carbapenemases to be recognized and since 2008 have been reported worldwide, mostly in bacteria from patients epidemiologically linked to the Indian subcontinent, where they occur widely in hospital and community infections, and also in contaminated urban water. The main type is NDM-1, but minor variants occur. NDM enzymes are present largely in Enterobacteriaceae, but also in non-fermenters and Vibrionaceae. Dissemination predominantly involves transfer of the blaNDM-1 gene among promiscuous plasmids and clonal outbreaks. Bacteria with NDM-1 are typically resistant to nearly all antibiotics, and reliable detection and surveillance are crucial.

Country-to-country transfer of patients and the risk of multi-resistant bacterial infection

Management of patients with a history of healthcare contact in multiple countries is now a reality for many clinicians. Leisure tourism, the burgeoning industry of medical tourism, military conflict, natural disasters, and changing patterns of human migration may all contribute to this emerging epidemiological trend. Such individuals may be both vectors and victims of healthcare-associated infection with multiresistant bacteria. Current literature describes intercountry transfer of multiresistant Acinetobacter spp and Klebsiella pneumoniae (including Klebsiella pneumoniae carbapenemase- and New Delhi metallo-β-lactamase-producing strains), methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and hypervirulent Clostridium difficile. Introduction of such organisms to new locations has led to their dissemination within hospitals. Healthcare institutions should have sound infection prevention strategies to mitigate the risk of dissemination of multiresistant organisms from patients who have been admitted to hospitals in other countries. Clinicians may also need to individualize empiric prescribing patterns to reflect the risk of multiresistant organisms in these patients.

Emergence of NDM-1 metallo-β-lactamase in Pseudomonas aeruginosa clinical isolates from Serbia

This work reports, for the first time, the presence of New Delhi metallo-β-lactamase 1 (NDM-1) in Pseudomonas aeruginosa. Moreover, this is the first report of the NDM-1 presence in the Balkan region. Cosmid gene libraries of carbapenem-nonsusceptible Pseudomonas aeruginosa clinical isolates MMA83 and MMA533 were screened for the presence of metallo-β-lactamases. Accordingly, both MMA83 and MMA533 carried the bla(NDM-1) gene. Pulsed-field gel electrophoresis (PFGE) analysis indicated that strains MMA83 and MMA533 belonged to different clonal groups. Five additional isolates from different patients clonally related to either MMA83 or MMA533 were found to be NDM-1 positive.

Complete sequencing of pNDM-HK encoding NDM-1 carbapenemase from a multidrug-resistant Escherichia coli strain isolated in Hong Kong

BACKGROUND

The emergence of plasmid-mediated carbapenemases, such as NDM-1 in Enterobacteriaceae is a major public health issue. Since they mediate resistance to virtually all β-lactam antibiotics and there is often co-resistance to other antibiotic classes, the therapeutic options for infections caused by these organisms are very limited.

METHODOLOGY

We characterized the first NDM-1 producing E. coli isolate recovered in Hong Kong. The plasmid encoding the metallo-β-lactamase gene was sequenced.

PRINCIPAL FINDINGS

The plasmid, pNDM-HK readily transferred to E. coli J53 at high frequencies. It belongs to the broad host range IncL/M incompatibility group and is 88803 bp in size. Sequence alignment showed that pNDM-HK has a 55 kb backbone which shared 97% homology with pEL60 originating from the plant pathogen, Erwina amylovora in Lebanon and a 28.9 kb variable region. The plasmid backbone includes the mucAB genes mediating ultraviolet light resistance. The 28.9 kb region has a composite transposon-like structure which includes intact or truncated genes associated with resistance to β-lactams (bla(TEM-1), bla(NDM-1), Δbla(DHA-1)), aminoglycosides (aacC2, armA), sulphonamides (sul1) and macrolides (mel, mph2). It also harbors the following mobile elements: IS26, ISCR1, tnpU, tnpAcp2, tnpD, ΔtnpATn1 and insL. Certain blocks within the 28.9 kb variable region had homology with the corresponding sequences in the widely disseminated plasmids, pCTX-M3, pMUR050 and pKP048 originating from bacteria in Poland in 1996, in Spain in 2002 and in China in 2006, respectively.

SIGNIFICANCE

The genetic support of NDM-1 gene suggests that it has evolved through complex pathways. The association with broad host range plasmid and multiple mobile genetic elements explain its observed horizontal mobility in multiple bacterial taxa.

Carbapenem resistance in Klebsiella pneumoniae due to the New Delhi Metallo-β-lactamase

Carbapenem resistance in Klebsiella pneumoniae is most notably due to the K. pneumoniae carbapenemase (KPC) β-lactamase. In this report, we describe the occurrence of a newly described mechanism of carbapenem resistance, the NDM-1 β-lactamase, in a patient who received medical attention (but was not hospitalized) in India.

Science, Names Giving and Names Calling: Change NDM-1 to PCM

A journal editor recently apologised for publishing a 2010 paper in which authors designated an enzyme as New Delhi metallo-β-lactamase-1 (NDM-1) and its related gene bla(NDM-1) after a city, New Delhi. This name had raised an outcry in India, with health authorities, media and medical practitioners demanding New Delhi be dropped from the name. The name was actually first given in another 2009 paper, whose corresponding author remains the same as the 2010 paper. There is a tradition of eponymous names in science. But those found derogatory to races, groups, cities, and countries have been changed. For example, "Mongolism" was changed to Down's syndrome; "Australia" antigen to HBsAg; "Mexican" Swine flu to H1N1; "GRID" (Gay Related Immune Deficiency) and 4H-Disease (Haitians, Homosexuals, Haemophiliacs and Heroin Users Disease) to AIDS. It is necessary that NDM-1 also be changed to a name based on scientific characteristics. NDM-1 must be changed to PCM (plasmid-encoding carbapenem-resistant metallo-β-lactamase). It is also necessary to review the tradition of naming organisms, diseases, genes, etc. after cities, countries and races. Often, such names giving amounts to names calling. It needs to be discarded by scientists in all new names giving from now on. "Geographical" and "racial" names giving must be replaced by "scientific" names giving. Journal editors must ensure that such scientific names giving is laid down as standard guideline in paper submissions. All such names still in currency need to be phased out by replacing them with names based on scientific characteristics, or in honour of their pioneering scientist/s or institutions. The lead author of the above 2010 paper has said he was not consulted about the final draft and did not agree with the conclusions of the paper. To ensure that corresponding authors do not ride roughshod over co-authors, and lead and other authors do not backtrack on papers, editors must ensure written concurrence of all authors, especially the lead author, to the final draft of a paper and include this in their guidelines for paper submissions.

Hospital epidemiology and infection control in acute-care settings

Health care-associated infections (HAIs) have become more common as medical care has grown more complex and patients have become more complicated. HAIs are associated with significant morbidity, mortality, and cost. Growing rates of HAIs alongside evidence suggesting that active surveillance and infection control practices can prevent HAIs led to the development of hospital epidemiology and infection control programs. The role for infection control programs has grown and continues to grow as rates of antimicrobial resistance rise and HAIs lead to increasing risks to patients and expanding health care costs. In this review, we summarize the history of the development of hospital epidemiology and infection control, common HAIs and the pathogens causing them, and the structure and role of a hospital epidemiology and infection control program.